PLACENTICERATID ®. 199 
sion between equally faint ridges. There is also a faint trace on the venter 
of the neanic stage, but it is then a single line sunk in the surface of the 
shell. It is too faint to be visible in any section, and is probably not present 
in the younger stages. 
In the neanic stage the rather large siphuncle is at a perceptible distance 
from the shell of the venter, but in the ephebie stage it is directly against 
it, and the double trace may be due to this. 
The sutures are more widely separated in Roemer’s figure than in my 
specimen, but this may be due to more vigorous growth. There were 
eleven saddles and ten lobes on the older sutures, with less complicated 
outlines than in pseudosyrtale, but otherwise similar. The sutures are well 
separated at all stages, but the last two are nearer together than the preced- 
ing. The ventral lobes are deeper and narrower and the siphonal saddles 
more prominent and distinct than in other species, except that described 
by Choffat m Portugal as P. whligi. It stands between this primitive form 
and P. pseudosyrtale and other American species, all of which have very 
broad ventral lobes and less prominent siphonal saddles. 
A very fine suite of this species was collected by Stanton and Vaughan, 
locality 1467, United States Geological Survey, San Carlos, Presidio 
County, Tex. The largest specimen is 204 mm. in diameter; a part of the 
aperture at the umbilical zone shows on one side and the length of the liy- 
ing chamber is somewhat less than one-half of a volution. The gerontic 
stage is present and the involution is considerably decreased along the outer 
‘sides of the nodes on their retreat from the umbilicus. The venter becomes 
broader and rounded on the last part of outer volution. The outer nodes 
change from round spines to elongated costee, dichotomous with the inner 
line of nodes that are nearly at the middle of the lateral zones at this age. 
There are some more compressed specimens that still, however, have 
very stout volutions and a prolonged stage, during which the venter becomes 
broadened and occupies the space between the second rows of nodes, the 
outer ventral rows forming lines on either side of a zone occupying the 
center of the ventral surface. These features are still like those of typical 
guadalupe, but in other cases it is impossible to say whether the specimens 
belong to typical guadalupe or to the next described species. 
Locality: San Carlos, Presidio County, Tex. 
Age: San Carlos beds, Upper Cretaceous. 
